Drive release and positive stop device

ABSTRACT

A gear mechanism for operating tap-changing regulating transformers includes means for automatically disconnecting a driven shaft from a driving shaft at predetermined limit positions of the tap-changing mechanism and to then arrest the driven shaft by positive action.

llnited States Patent [151 3,635,319

Bleibtreu et al. 1 Jan. 1, 1972 [54] DRIVE RELEASE AND POSITIVE STOP DEVICE [56] References Cited [72] Inventors: Alexander Bleibtreu, 84 Regensburg, Roter UNITED STATES PATENTS Brachweg 65 Josef Neumayer, 8401 Kqfering Buchhauser Siedling 156, near Regen 1,765,527 6/1930 Gollmck et al. ..192/28 burgq'bmh of Germany 1,919,651 7/1933 Helsel ..192/28 3,173,392 3/1965 l-ledegaard ..192/28 [22] Filed: Aug. 18, 1970 [21] APP] No; 64,756 Primary ExaminerAllan D. l-lerrmann Attorney-Erwln Salzer [30] Foreign Application Priority Data [57] ABSTRACT Oct. 3, Germany A gear mechanism for operating [ap.changing regulating transformers includes means for automatically disconnecting U-S. a driven from a driving haft at predetermined i. 192/148 tions of the tap-changing mechanism and to then arrest the [51 Int. Cl ..F16d 65/30, Fl6d 71/00 driven shaft by positive action [58] FieldofSearch ..192/l5,28,35,36,33,71, 192/ 148, 149 22 Claims, 6 Drawing Figures l i i. J5 J 1' 55 E X7 M 35 T 1 I I PATENTEnJAmm 3.635.319

SHEET 2 [1F 4 BACKGROUND OF INVENTION It is often desirable to limit the range within which a tapchanging regulating transformer is allowed to operate. In other words, in such instances the range within the selector switch of a tap-changing regulating transformer is allowed to operate is subjected to predetermined limits which ought not to be exceeded, though the range of taps, and consequently the range of possible tap-changes which could be achieved with a particular piece of equipment, may be larger than a predetermined narrower range of tap-changes deemed desirable, or permissible, in any particular instance;

One way to arrest the driven shaft of a gear mechanism for operating a tap-changing regulating transformer at a given limit position is to stop rotation of the shaft by positive action when the limit position is reached. This method, and devices for carrying it into effect, as evolved to-date are subject to serious drawbacks. One of these drawbacks is their criticality. In such gear mechanisms the electric motor drive must be deenergized by means of limit switches shortly before the driven shaft is stopped by positive action. Such limit switches fail sometimes, in which case the electric driving motor is subject to a violent mechanical shock and then energized by the locked-rotor current. This, in turn, calls for a motor starter provided with overload tripping means to preclude damage to the motor. Because of these drawbacks it isnot desirable to limit the operation of tap-changing regulating transformers in the way set forth above by the prior art positive action devices restraining the movement of the driven shaft.

Another method of precluding operation of a tap-changing regulating transformer beyond a predetermined limit position consists in providing coupling means between the driving shaft and the driven shaft inhibiting further transmission of torques from the former to the latter when the tap-changing regulating transformer, and more particularly the selector switch thereof, have reached a predetermined limit position. Such priorv art drives for tap-changing regulating transformers are bulky, complex and expensive. In addition to thesedrawbacks such drives are rather unreliable since they have a tendency to allow continued motion of the driven portion of the gear mechanism due to its inertia and inherent kinetic energy.

SUMMARY OF INVENTION The invention relates to gears for operating tap-changing regulating transformers within predetermined limit positions which combine the advantages of prior art .gears of this description and eliminate the drawbacks of such prior art gears.

A gear drive embodying this invention includes a driving shaft and a driven shaft. A gear is arranged in coaxial relation to and rotatable relative to the driven shaft. This gear is driven by the driving shaft and has latching means projecting axially outwardly from one of the end surfaces thereof. The gear drive further includes a hub member fixedly mounted on said driven shaft for joint rotation with said driven shaft,'and being provided with abutment surfaces. A latching element is arranged between said gear and said hub member acted upon by said latching means of said gear. This latching element'ineludes means for transmitting torques from said gear to both said hub member and said driven shaft, andsaid latching element is further provided with an abutment means. The structure further includes a coupling member loosely mounted on said driven shaft and rotatable-though but to a limited extent-relative to said driven shaft. The aforementioned coupling member has abutment means arranged to engage said abutment means on said latching element, and to be engaged by said abutment surfaces of said hub member, thus limiting the freedom of relative rotary motionof said coupling member and said hub member. In addition to the above a gear structure embodying this inventionincludes normally ineffective latching means for the aforementioned coupling member. These latching means are movable from an ineffective position thereof to an effective position. In the latter they restrain by positive action rotary movement of the coupling member,

and they restrain also by positive action rotary movement of both the hub member and the driven shaft upon engagement of one of said abutment surfaces of said hub member by said abutment means of said coupling member.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is substantially a side elevation of a gear drive embodying the present invention. some parts of the same being broken away to expose to view other parts thereof;

FIG. 2 is a cross section of the structure of FIG. 1 taken along "-11 of FIG. 1;

FIG. 3 is a cross section of the structure of FIG. 1 taken along III-III of FIG. 1;

FIG. 4 is a top-plan view of the structure of FIG. 1, some parts of that structure situated at a relatively high level thereof having been deleted in FIG. 4;

FIG. 5 is an exploded isometric view of some of the parts of the structure of FIG. 1; and

FIG. 6 is a section along VI-VI of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawings, reference numeral 10 has been applied to indicate a gear housing covered by housing cover 11 having an aperture at the top surface thereof. Housing 10 is filled with oil to lubricate the movable parts which are arranged therein. Reference numeral 12 has been applied to indicate a driving shaft and reference numeral 13 has been applied to indicate a driven shaft driven by driving shaft 12. Both shafts 12,13 are supported by bearings which, in turn, are supported by gear housing 10. Gear 15 is arranged in coaxial relation which shaft 13 and is driven by shaft 12. Driven shaft 13 supports gear 15 by the intermediary of roller bearings 14. Thus gear 15 is freely rotatable relative to driven shaft 13, and vice versa. Since gear 15 isloosely mounted on shaft 13 both are arranged in coaxial relation. Gear 15 combines a spur gear means 151 an a bevel gear means 152. Spur gear means 151 meshes with pinion l6 fixedly mounted on driven shaft 12 operated by the electric motor drive 19. Bevel .gear means 152 meshes with another bevel gear 17 fixedly mounted on a driving shaft 18. The latter is intended for manuallyoperating the mechanism whenever such operation is required. To this end shaft 18 may be provided with manually operable crank (not shown)..

Gear 15 is provided with an abutment member or latching means 20 projecting axially outwardly from one of the end surfaces of gear 15. Reference numeral 21 has been applied to indicate a substantially annular latchingelement having two abutment or latching surfaces 210. Driven shaft 13 projects transversely through the opening defined by latching element 21. The two surfaces 210 of latching element 21 are intended to be engaged by cooperating surfaces of abutment member or latching means 20. FIGS. 2 and 3 show clearly how one of the surfaces 210 is engaged by one cooperating surface of abutment member or latching means 20 integral with gear 15.

Reference numeral 22 has been applied to indicate a crank having a hub member 221 fixedly mounted on driven shaft 13 and jointly rotatable with the latter. Crank 22 is provided with a pin 13 projecting axially away from crank 22 and forming a fulcrum for annular latching element 21. Latching element 21 is provided with a circular bore 21' juxtaposed to, or aligned with, pin 23 and receiving pin 23. Crank 22 has two abutment surfaces 220 extending substantially radially relative to shaft 13 each intended to cooperate with, i.e., to be engaged by, one corresponding abutment surface 30 of a coupling member 26 which is described below more in detail. Annular latching element 21 supports on the upper end surface thereof a hollow cylindrical axially extending projection 250. This projection performs two functions. It forms an abutment integral with latching element 21 and it further forms a brake housing receiving brake block 25 and its helical biasing spring 24.

Brake block 25 frictionally engages the upper end surface of gear 15.

Gear housing cover 11 supports a roller bearings 27 which, in turn, supports a coupling member 26. Driven shaft 13 projects through coupling member 26 and the latter is loosely mounted on the former. Thus parts 13 and 26 are relatively rotatable. As will be explained below more in detail there is, however, a limited freedom of rotation of coupling member 26 relative to both driven shaft 13 and hub member 221. Coupling member 26 is substantially in the shape of a toroid, and provided with a radially outwardly projecting flange 28. The upper end of coupling member 26 is provided with a latch 29 and the flange portion 28 of coupling member 26 is provided with a pair of coupling claws or dogs 30 which are angularly displaced 180.

FIG. shows latch 29 but in a diagrammatic fashion, while FIG. 1 shows parts 26 and 29 more in detail. It is apparent from FIG. 1 that the coupling member 26 and the latch 29 are two distinct parts as indicated by different hatching thereof. Latch 29 includes a radially inner annular portion which is mounted on the coupling member 26 proper. The aforementioned radially inner annular portion of latch 29 is keyed to coupling member 26 proper so as to preclude any relative pivotal motion between parts 26 and 29. As far as this invention is concerned, it is immaterial whether or not parts 26 and 29 are two separate parts tied together, as explained above in connection with FIG. 1, or are a unitary structure, as suggested by FIG. 5.

The dogs or claws 30 of coupling member 26 are arranged to cooperate with, or engage with, the abutment surface 220 on crank 22 and to cooperate with, or engage with, brake housing 250 on latch 21. Latch 29 and coupling member 26 are normally free to rotate jointly with driving shaft 13, a torque being transmitted from the upper end surface of part 221 to flange 28 in frictional engagement with part 221. Parts 26,29 may be restrained by cooperating latch 31. Latch 31 is supported by a leaf spring 32 tending to maintain latch 31 in the median position thereof shown in FIG. 4. In that position latches 31 and 29 are out of engagement, and parts 29,26 are free to rotate jointly with driven shaft 13 and hub member 221. FIG. 6 shows latch 31 displaced out of its median position of FIG. 4, in cooperative engagement with latch 29 and thus precluding continued rotation of parts 29 and 26 jointly with driven shaft 13 and hub member 221.

Reference character 34 (see FIG. 1) has been applied to indicate a pair of cooperating spur gears of which the smaller is fixedly mounted on a portion of driven shaft 13 projecting through coupling member 26 out of gear housing 10. The larger of the two meshing spur gears 14 is provided on the lower end surface thereof with a pair of angularly displaced abutment pins 35. Abutment pins 35 cooperate with a pivotable system of levers 33. Upon being engaged by one of pins 35 the lever system 33 pivots to its position shown in FIG. 6 and in so doing moves latch 31 out of its median position or ineffective position into its latching position or effective position wherein it engages latch 29 and restrains by positive action parts 29 and 26, thus causing cessation of the rotary motion thereof.

The driven shaft 13 operates a tap-changing regulating transformer, and more particularly the selector switch thereof not shown in the drawings. This is achieved by the interpositionof additional gear means, as shown more in detail in US. Pat. No. 3,176,089 to A. Bleibtreu et al. Mar. 30, 1965 for LOAD TAP CHANGERS FOR TRANSFORMERS, in U.S. Pat. No. 3,299,049 to A. Bleibtreu, Feb. I, 1966 for IN- TEGRAL SELECTOR SWITCH AND TRANSFER SWITCH UNIT FOR TAPPED REGULATING TRANSFORMERS, and in US. Pat. No. 3,396,254 to A. Bleibtreu, Aug. 6, 1968 for ARRANGEMENT FOR AVOIDING EDDY CURRENT LOSSES IN TRANSFER SWITCH AND SELECTOR SWITCH UNITS WITH INTERPOSED GEAR DRIVE. When the selector switch reaches a particular tap of a tapped transformer winding beyond which the selector switch is not supposed to operate, i.e., at which point the tap-changing drive of the selector switch is supposed to be stopped, the larger of spur gears 34 has been turned by the smaller of spur gears 34, or pinion, about such an angle that one of the pins 35 of the former engages and pivots lever system 33. As a result, the system of levers 33 acts upon leaf spring 32 and moves latch 31 out of its median ineffective position shown in FIG. 4 to one of its offcenter positions or effective positions of which one is shown in FIG. 6. In that position latch 31 engages latch 29 on coupling member 26. This precludes further rotation of coupling member 26 jointly with driven shaft 13 and hub member 221. In the arrested position of coupling member 26 one of its claws or dogs 30 is engaged by the cap or brake housing 250 of latching element 21. This precludes any further movement of latching element 21 at the point of engagement ofparts 30 and 250. On the other hand, latching element 21 is still free to move at the point thereof diametrically opposite to the abutment surface thereof formed by hollow cylindrical cap or brake housing 250. This point is actually moved by virtue of the cooperative engagement of projection or latching means 20 of spur gear 15 with one of the cooperating abutment surfaces 210 on latching element 21, spur gear 15 being driven by spur gear 16 and motor 19. As a result of the aforementioned movement of latching element 21 under the action of projection of latching means 20 of spur gear 15, 'the engaging surfaces of projection or latching means 20 and of latching element 21 are disengaged, and thus latching element 21 comes to rest. Since crank 22 and driven shaft 13 are driven by spur gear 15 by the intermediary of latching element 21, crank 22 and driven shaft 13 come also to rest when latching element 21 comes to rest. Driving shafts 12 and 18, respectively, continue to rotate after crank 22 and driven shaft 13 have come to rest. In other words, when parts 20 and 21 come out of engagement, driven shaft 13 is disconnected from driving shafts l2 and 18, respectively, so that no torque is transmitted any longer to the former from the latter.

This completes the first step or phase of the process of arresting driven shaft 13. The second step or phase in the process of arresting driven shaft 13 consists in precluding by positive action any further rotation of driven shaft 13. Driven shaft 13 is precluded by positive action from further rotation by virtue of an engagement of one of the abutment surfaces 220 of crank 22 by one of the abutment surfaces, dogs, or claws 30 of coupling member 26. This limit position has been shown in FIG. 3, where the upper abutment surface, dog, or claw 30 is shown to be engaged by the upper abutment surface 220 of crank 22, both engaging surfaces being indicated in this figure in dotted lines.

It may be added in this context that in the position of parts shown in FIG. 3 coupling member 26 and its claws 30 cannot rotate since it is restrained by cooperative engagement of latches 29 and 31, and shaft 13 cannot rotate since one of surfaces 220 of crank 22 which is fixedly mounted upon shaft 13 is engaged by one of claws 30 of coupling member 26.

In any end position of driven shaft 13 motor 19 is deenergized by means of limit switches (not shown).

When it is intended to operate the tap-changing switch mechanism under the control of driven shaft 13 in the reverse direction electric motor 19 is reenergized to operated spur gears 16 and 15 in a direction opposite to that in which they have been operated before the gear mechanism reached the limit position shown in FIG. 3. The ensuing rotary motion of gear 15 is transmitted to latch 21 by the intermediary of brake block 25, and this causes relatching of latching element 21 with the axial projection or latching means 20 of spur gear 15. Thus the torque of spur gear 15 is transmitted to driven shaft 13 by the intermediary of latching element 21 and pin 23 of crank 22 and driven shaft 13 may be rotated until the tap changing switch mechanism reaches its other limit position causing engagement of the lower latch surface of latch 31 as seen in FIG. 6 with the right latch surface of latch 29 as seen in the same figure. This, in turn, causes sequential disconnection of driving shafts 12 and 18, respectively, from driven shaft 13, and subsequent blocking of driven shaft 13 by positive action.

The following is a brief summary of the mode of operation of the structure of FIGS. 1-6:

1 Gears 34 operate pins 35. One of pins 35 operates lever system 33. Lever system 33 latches latching mechanism 31,29 thus arresting coupling member 26 and itsclaws 30. One of claws 30 engages abutment 250 causing unlatching of parts 20 and 21, 210. This disconnects latching element 21, crank 22, hub member 221 and driven shaft 13 from the source of power or electric motor 19. Thereupon crank 22 and driven shaft 13 are arrested by positive action resulting from engagement of one of surfaces 220 by one of claws 30, claws 30 being restrained by the action of latching mechanism 29,31.

There is a time element involved in the pivotal movement of latching element 20 about part 250 and the concomitant disengagement of one of latching surfaces 210 of latching element 21 from the latching means 20 of spur gear 15. This short period of time is substantially equal to the short period of time during which there is a relative motion between driven shaft 13 and hub member 221, on the one hand, and coupling member 26, on the other hand, which results in an abutting engagement of one of surfaces 220 and one of dogs or claws It is apparent from FIG. 1 that coupling member 26 includes a portion situated inside of the space bounded by gear housing 111 and housing cover 11 and another portion situated outside the aforementioned space. The latch 29 is situated outside that space. It will be further apparent from FIGS. 1 and 5 that the lower end surface of flange 28 of coupling member 26 and the upper end surface of crank 22 and hub member 221 are arranged in a common plane and hence in frictional engagement with each other. The dog surfaces 30 and their cooperating surfaces 220 on hub member 221 and crank 22, respectively, limit the freedom of relative motion between coupling member 26 and shaft 13.

' As clearly shown in FIG. 2 the size the opening defined by latching element 21 and the outer diameter of hub member 221 are so coordinated as to cause cooperative abutting engagement of hub member 221 and the radially inner edge of latching element 21 upon engagement by one of abutment means or dogs 30 of coupling member 26 by one of the abutment surfaces 220 of hub member 221.

At the time when the cooperating surfaces 20 and 210 are disengaged and electromotor 19 deenergized one of surfaces 220 engages one of dogs 30. When motor 19 is reenergized and begins to rotate in the reverse direction the same surface 220 remains initially in engagement with the same dog 30, torque being transmitted from part 221,22 to parts 28,26 by virtue of the frictional engagement thereof. When parts 28,26 are arrested by the positive action of latches 31,29, the surface 220 previously in engagement with one of dogs 30 moves out of engagement with that dog, and the other surface 220 moves into engagement with the other dog 30.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the invention, and it is, therefore, aimed to cover all such changes and modification as fall within the spirit and scope of the invention.

What is claimed is:

1. A gear drive for tap-changing regulating'transformers including a. a driving shaft (12,18);

b. a driven shaft (13);

c. a gear (15 arranged in coaxial relation to, and rotatable relative to, said driven shaft (13) and driven by said driving shaft (12,18), said gear (15) having latching means projecting axially outwardly from one of the end surfaces thereof;

d. a hub member (221) fixedly mounted on said driven shaft (13) for joint rotation with said driven shaft (13) and being provided with abutment surfaces (220);

e. a latching element (21) arranged between said gear (15) and said hub member (22) cooperating with said latching means (20) of said gear (15) and including means (21,23) for transmitting torques from said 'gear (15) to both said hub member (221) and driven shaft (13), said latching element (21) being further provided with an abutment means (250);

f. a coupling member (26) loosely mounted on said driven shaft (13) and pivotable relative to said driven shaft 13), said coupling member (26) having abutment means (30) arranged to engage said abutment means (250) of said latching element (21) and to be engaged by said abutment surfaces (220) of said hub member (221); and

g. normally ineffective latching means (31,29) for said coupling member (26) movable from an ineffective position thereof to an effective position thereof to restrain rotary movement of said coupling member (26) and to restrain rotary movement of both said hub member (221) and said driven shaft (13) upon engagement of said abutment means (30) of said coupling member (26) by one of said abutment surfaces (220) of said hub member (221).

2. A gear drive as specified in claim 1 wherein said gear (15) is a dual function gear provided with spur gear means (151) and with bevel gear means (152), one of said gear means meshing with motor driven gear (16) and the other of said gear means meshing with a manually driven gear (17).

3. A gear drive as specified in claim 2 wherein said spur gear means (151) mesh with a motor driven spur gear (16) and wherein said bevel gear means (152) mesh with a manually operable bevel gear (17).

4. A gear drive as specified in claim 1 wherein said latching element (21) is substantially annular, wherein said driven shaft (13) projects through the opening defined by said annular latching element (21), and wherein said hub member (221) has an outer diameter of such size as to cause cooperative engagement of said hub member (221) and of the radially inner edge of said annular latching element (21) upon engagement by said abutment means (30) of said coupling member (26) of one of said abutment surfaces (220) of said hub member (221).

5. A gear drive as specified in claim 1 wherein said abutment means (250) of said latching element (21) is formed by a hollow cylindrical projection (250) housing a spring-biased brake mechanism (24,25) including a brake block (25) frictionally engaging said one of the end surfaces of said gear 6. A gear drive as specified in claim 1 wherein said coupling member (26) is provided with a flange (28) having a larger diameter than said coupling member, wherein said flange (28) is provided with said abutment means (30), and wherein said abutment means (30) are formed by a pair of claws.

7. A gear drive as specified in claim 1 wherein said gear (15), said hub member (221), and said latching element (21) are arranged in a gear housing (10) being closed by a cover (11) and wherein said coupling member (26) projects from the space bounded by said gear housing (10) and said cover (11) through an opening defined by said cover (11) to the space outside of said gear housing (10) and said cover (1 1).

8. A gear drive for tap-changing regulating transformers having a driving shaft, a driven shaft operated by said driving shaft and a coupling mechanism interposed between said driving shaft and said driven shaft, said coupling mechanism including a. a gear (15) loosely mounted on said driven shaft (13) and rotatable relative to said driven shaft (13), said gear (15) having a torque-transmitting projection (20) extending axially outwardly from one of the end surfaces thereof;

b, an annular latching element (21) having a pair of latching surfaces (210) cooperating with said projection (20) of said gear (15) to transmit torques from said gear (15) to said latching element (21 said latching element (21) being further provided with an abutment means (250) projecting axially outwardly from said latching element;

c. a crank (22) mounted on said driven shaft (13) for joint rotation with said driven shaft (13), said crank including fulcrum means (23) pivotally connecting said crank (22) to said latching element (21), and said crank further including a pair of substantially radially oriented abutment surfaces (220);

d. a coupling member (26) loosely mounted on said driven shaft (13) and pivotable relative to said driven shaft (13), said coupling member (26) having a pair of dogs (30) arranged to engage said abutment means (250) of said latching element (21) and to be engaged by said abutment surfaces (220) of said crank (22); and

e. normally ineffective latching means (31,29) for said coupling member (26) movable from an ineffective position thereof to an effective position thereof to restrain rotary movement of said coupling member (26) and to further restrain rotary movement of both said crank (22) and said driven shaft (13) upon engagement of one of said abutment surfaces (220) of said crank (22) by one of said pair ofdogs (30) of said coupling member (26).

9. A gear drive as specified in claim 8 wherein said gear (15) is a dual function gear provided with a pair of gear means, one of said pair of gear means being a spur gear means (151) and the other of said gear means being a bevel gear means (152), and wherein one of said pair of gear means is adapted to be driven by motor means (19) and the other of said pair of gear means is adapted to be driven manually.

10. A gear drive as specified in claim 8 wherein said latching element (21) is provided with a cylindrical bore (21') and wherein said crank (22) includes a pin (23) projecting into said bore (21') of said latching element (21) pivotally connecting said latching element (21) and said crank (22).

11. A gear drive as specified in claim 8 wherein the inner diameter of said annular latching element (21) and the outer diameter of a hub (221) of said crank (22) mounted on said driven shaft (13) are coordinated in such a way that said hub (221) of said crank (22) engages said annular latching element (21) upon engagement of one of said pair of abutment surfaces (220) of said crank (22) by one of said pair of dogs (30) of said coupling member (26).

12. A gear drive as specified in claim 8 wherein said abutment means (250) of said annular latching element (21) is formed by a cylindrical projection extending from the side of said annular latching element (21) remote from said gear (15) and housing a biasing spring (24) and a brake block (25) biased by said spring (24) and engaging the end surface of said gear (15) adjacent said latching element (21).

13. A gear drive as specified in claim 8 wherein said coupling member (26) includes a portion of relatively small diameter provided with a latch (29) on the radially outer surface thereof and a flange portion (28) of relatively large diameter, said pair of dogs (30) projecting axially from the end surface of said flange portion (28) adjacent said crank (22).

14. A gear drive as specified in claim 13 wherein said gear (15 said latching element (21) and said flange portion (28) of said coupling member (26) are arranged within a gear housing provided with a cover (11), wherein said portion of said coupling element (26) of relatively small diameter projects through said cover (11) to the outside of the space defined by said gear housing (10) and by said cover (11), and wherein said latch (29) is situated outside of said space defined by said gear housing (10) and said cover (11).

15. A gear drive as specified in claim 8 including a. a gear of relatively small diameter fixedly mounted on said driven shaft (13) for joint rotation with said driven shaft (13);

b. a gear of relatively large diameter in meshing engagement with said gear of relatively small diameter, said gear of relatively large diameter being provided with a pair of angularly displaced abutment means (35);

c. a lever system (33) operable by said abutment means (35) of said gear of relatively large diameter upon a predetermined number of revolutions of said driven shaft (13); and

d. a latch (31) operated by said lever system (33) cooperating with said latch (29) on said radially outer surface of said portion of relatively small diameter of said coupling member (26) to arrest said coupling member (26) upon engagement of said last mentioned latch (29) by said first mentioned latch (31).

16. A gear drive for tap-changing regulating transformers including a. a driving shaft (12,18);

b. a driven shaft (13);

c. a gear (15) arranged in coaxial relation to and rotatable relative to said driven shaft (13) and driven by said driving shaft (12,18);

d. a hub member (221 fixedly mounted on said driven shaft (13) for joint rotation with said driven shaft 13) and including a pair of abutment surfaces (220) projecting substantially radially outwardly from said driven shaft (13);

e. a coupling member (26) having a surface in abutting relation with said hub member (221) and being loosely mounted on said driven shaft (13), said coupling member (26) having abutment means (30) cooperating with said abutment surfaces (220) of said hub member (221) to limit the freedom of relative rotary motion of said coupling member (26) on the one hand, and said hub member (26) and said driven shaft (13), on the other hand,

f. normally ineffective latching means (31,29) for said coupling member (26) movable from an ineffective position to an effective position thereof and compelling in said effective position by positive mechanical action cessation of the rotary motion of said coupling member (26); and

g. combined latching and torque-transmitting means (20,2l,22,23) normally effective to transmit torques from said gear (15) to both said hub member (221) and said driven shaft (13), said combined latching and torque-transmitting means (20,21,22,23) including means (250) responsive to said cessation of said rotary motion of said coupling member (26) to render said combined latching and torque-transmitting means (20,21,22,23) ineffective to cause cessation of transmission of torques from said gear (15) to both said hub member (221) and said driven shaft (13) upon said cessation of said rotary motion of said coupling member (26).

17. A gear drive for tap-changing regulating transformers as specified in claim 16 wherein said combined latching and torque-transmitting means include a. a substantially annular latching element (21) surrounding said driven shaft (13) and having an abutment means (250) projecting axially outwardly from a plane defined by said latching element (21) and arranged to be engaged by said abutment means (30) of said coupling member (26), said latching element (21) being provided with means (2l,23,22) pivotally connecting said latching element (21) to said hub member (221), and said latching element (21) being further provided with a pair of latching surfaces (210) arranged to opposite sides of said means (2l,23,22) pivotally connecting said latching element (21) to said hub member (221), and wherein b. said gear (15) is provided with a torque-transmitting projection (20) on the end surface thereof adjacent said annular latching element (21) cooperating with said pair of latching surfaces (210) thereof.

18. A gear drive as specified in claim 18 wherein said abutment means (250) is hollow and houses a brake mechanism including a spring (24) and brake block (25) biased by said spring (24) and frictionally engaging said end surface of said gear (15) adjacent said annular latching element (21 19. A gear drive as specified in claim 16 including a. a gear housing (10) and a cover (11) therefore having an aperture on one side thereof, said gear (15), said hub member (221) and said combined latching and torquetransmitting means (20,21,22,23) being arranged inside of the space bounded by said gear housing (10) and said cover (11), and said coupling member (26) being arranged in part inside of aid space and in part outside of said space and projecting through said aperture in said cover; and

b. a mechanical power transmission (34,35,33) arranged outside of said space, said transmission being operated by one end of said driven shaft (13) projecting through said coupling member (26) to the outside of said space and said transmission (34,35,33) controlling said normally ineffective latching means (3l,29) to render said normally ineffective latching means effective upon a predetermined number of revolutions of said driven shaft (13).

20. A gear drive for tap-changing regulating transformers including a. a driving shm (12,18) supporting a driving gear (16,17);

b. a driven shaft (13);

c. a gear (15) arranged in coaxial relation to said driven shaft (13), rotatable relative to said driven shaft (13) and driven by said driving gear (16,17);

d. a hub member (221) fixedly mounted on said driven shaft (13) for joint rotation with said driven shaft (13);

e. a coupling member (26) loosely mounted on said driven shaft (13) in torque-transmitting relation with said hub member (221);

f. cooperating abutment means (220,30) on said hub member (221) and on said' coupling member (26) for limiting the amount of relative rotary motion of said hub member (221) and of said coupling member (26);

g. normally ineffective latching means (31,29) for said coupling member (26) movable from an ineffective position to an effective position thereof and compelling in said effective position by positive action cessation of rotary motions of said coupling member (26) about said driven shaft (13); h. means (34,35,33) responsive to the rotary motion of said driven shaft (13) for moving said normally ineffective latching means (31,29) from said ineffective position to said effective position;

i. combined latching and torque-transmitting means (20,21,22,23) interposed between said gear 15) and said hub member (221) for torque transmission from said gear (15) to said hub member (221 and j. means under the control of said coupling member (26) engaging said combined latching and torque-transmitting means (20,21,22,23) upon said cessation of rotary motion of said coupling member (26) about said driven shaft (13) and thereby unlatching said combined latching and torque-transmitting means (20,2l,22,23) to preclude further torque transmission from said gear (15) to said hub member (221).

21. A gear drive as specified in claim 20 wherein said combined latching and torque-transmitting means include a. a substantially annular latching element (21) surrounding said driven shaft (13) and having a pair of latching surfaces (210) engageable by cooperating latching surfaces (20) on said gear (15); and

b. a pin (23) pivotally connecting said annular latching element (21) and said hub member (221) and wherein c. said coupling member (26) is provided with an abutment (30) arranged to engage a cooperating abutment surface (250) on said annular latching element (21) to cause disengagement of one of said pair of latching surfaces (210) of said annular latching element (21) from said cooperating latching surfaces (20) on said gear 15).

22. A gear drive as specified in claim 21 including means in the nature of a friction brake (24,25) supported by said annular latching element (21) establishing a frictional connection between said annular latching element (21) and said gear (15 

1. A gear drive for tap-changing regulating transformers including a. a driving shaft (12,18); b. a driven shaft (13); c. a gear (15) arranged in coaxial relation to, and rotatable relative to, said driven shaft (13) and driven by said driving shaft (12,18), said gear (15) having latching means (20) projecting axially outwardly from one of the end surfaces thereof; d. a hub member (221) fixedly mounted on said driven shaft (13) for joint rotation with said driven shaft (13) and being provided with abutment surfaces (220); e. a latching element (21) arranged between said gear (15) and said hub member (22) cooperating with said latching means (20) of said gear (15) and including means (21,23) for transmitting torques from said gear (15) to both said hub member (221) and driven shaft (13), said latching element (21) being further provided with an abutment means (250); f. a coupling member (26) loosely mounted on said driven shaft (13) and pivotable relative to said driven shaft (13), said coupling member (26) having abutment means (30) arranged to engage said abutment means (250) of said latching element (21) and to be engaged by said abutment surfaces (220) of said hub member (221); and g. normally ineffective latching means (31,29) for said coupling member (26) movable from an ineffective position thereof to an effective position thereof to restrain rotary movement of said coupling member (26) and to restrain rotary movement of both said hub member (221) and said driven shaft (13) upon engagement of said abutment means (30) of said coupling member (26) by one of said abutment surfaces (220) of said hub member (221).
 2. A gear drive as specified in claim 1 wherein said gear (15) is a dual function gear provided with spur gear means (151) and with bevel gear means (152), one of said gear means meshing with motor driven gear (16) and the other of said gear means meshing with a manually driven gear (17).
 3. A gear drive as specified in claim 2 wherein said spur gear means (151) mesh with a motor driven spur gear (16) and wherein said bevel gear means (152) mesh with a manually operable bevel gear (17).
 4. A gear drive as specified in claim 1 wherein said latching element (21) is substantially annular, wherein said driven shaft (13) projects through the opening defined by said annular latching element (21), and wherein said hub member (221) has an outer diameter of such size as to cause cooperative engagement of said hub member (221) and of the radially inner edge of said annular latching element (21) upon engagement by said abutment means (30) of said coupling member (26) of one of said abutment surfaces (220) of said hub member (221).
 5. A gear drive as specified in claim 1 wherein said abutment means (250) of said latching element (21) is formed by a hollow cylindrical projection (250) housing a spring-biased brake mechanism (24,25) including a brake block (25) frictionally engaging said one of the end surfaces of said gear (15).
 6. A gear drive as specified in claim 1 wherein saiD coupling member (26) is provided with a flange (28) having a larger diameter than said coupling member, wherein said flange (28) is provided with said abutment means (30), and wherein said abutment means (30) are formed by a pair of claws.
 7. A gear drive as specified in claim 1 wherein said gear (15), said hub member (221), and said latching element (21) are arranged in a gear housing (10) being closed by a cover (11) and wherein said coupling member (26) projects from the space bounded by said gear housing (10) and said cover (11) through an opening defined by said cover (11) to the space outside of said gear housing (10) and said cover (11).
 8. A gear drive for tap-changing regulating transformers having a driving shaft, a driven shaft operated by said driving shaft and a coupling mechanism interposed between said driving shaft and said driven shaft, said coupling mechanism including a. a gear (15) loosely mounted on said driven shaft (13) and rotatable relative to said driven shaft (13), said gear (15) having a torque-transmitting projection (20) extending axially outwardly from one of the end surfaces thereof; b. an annular latching element (21) having a pair of latching surfaces (210) cooperating with said projection (20) of said gear (15) to transmit torques from said gear (15) to said latching element (21), said latching element (21) being further provided with an abutment means (250) projecting axially outwardly from said latching element; c. a crank (22) mounted on said driven shaft (13) for joint rotation with said driven shaft (13), said crank including fulcrum means (23) pivotally connecting said crank (22) to said latching element (21), and said crank further including a pair of substantially radially oriented abutment surfaces (220); d. a coupling member (26) loosely mounted on said driven shaft (13) and pivotable relative to said driven shaft (13), said coupling member (26) having a pair of dogs (30) arranged to engage said abutment means (250) of said latching element (21) and to be engaged by said abutment surfaces (220) of said crank (22); and e. normally ineffective latching means (31,29) for said coupling member (26) movable from an ineffective position thereof to an effective position thereof to restrain rotary movement of said coupling member (26) and to further restrain rotary movement of both said crank (22) and said driven shaft (13) upon engagement of one of said abutment surfaces (220) of said crank (22) by one of said pair of dogs (30) of said coupling member (26).
 9. A gear drive as specified in claim 8 wherein said gear (15) is a dual function gear provided with a pair of gear means, one of said pair of gear means being a spur gear means (151) and the other of said gear means being a bevel gear means (152), and wherein one of said pair of gear means is adapted to be driven by motor means (19) and the other of said pair of gear means is adapted to be driven manually.
 10. A gear drive as specified in claim 8 wherein said latching element (21) is provided with a cylindrical bore (21'') and wherein said crank (22) includes a pin (23) projecting into said bore (21'') of said latching element (21) pivotally connecting said latching element (21) and said crank (22).
 11. A gear drive as specified in claim 8 wherein the inner diameter of said annular latching element (21) and the outer diameter of a hub (221) of said crank (22) mounted on said driven shaft (13) are coordinated in such a way that said hub (221) of said crank (22) engages said annular latching element (21) upon engagement of one of said pair of abutment surfaces (220) of said crank (22) by one of said pair of dogs (30) of said coupling member (26).
 12. A gear drive as specified in claim 8 wherein said abutment means (250) of said annular latching element (21) is formed by a cylindrical projection extending from the side of said annular latching element (21) remote from said gear (15) and housing a biasing spring (24) and a brake block (25) biased By said spring (24) and engaging the end surface of said gear (15) adjacent said latching element (21).
 13. A gear drive as specified in claim 8 wherein said coupling member (26) includes a portion of relatively small diameter provided with a latch (29) on the radially outer surface thereof and a flange portion (28) of relatively large diameter, said pair of dogs (30) projecting axially from the end surface of said flange portion (28) adjacent said crank (22).
 14. A gear drive as specified in claim 13 wherein said gear (15), said latching element (21) and said flange portion (28) of said coupling member (26) are arranged within a gear housing (10) provided with a cover (11), wherein said portion of said coupling element (26) of relatively small diameter projects through said cover (11) to the outside of the space defined by said gear housing (10) and by said cover (11), and wherein said latch (29) is situated outside of said space defined by said gear housing (10) and said cover (11).
 15. A gear drive as specified in claim 8 including a. a gear of relatively small diameter fixedly mounted on said driven shaft (13) for joint rotation with said driven shaft (13); b. a gear of relatively large diameter in meshing engagement with said gear of relatively small diameter, said gear of relatively large diameter being provided with a pair of angularly displaced abutment means (35); c. a lever system (33) operable by said abutment means (35) of said gear of relatively large diameter upon a predetermined number of revolutions of said driven shaft (13); and d. a latch (31) operated by said lever system (33) cooperating with said latch (29) on said radially outer surface of said portion of relatively small diameter of said coupling member (26) to arrest said coupling member (26) upon engagement of said last mentioned latch (29) by said first mentioned latch (31).
 16. A gear drive for tap-changing regulating transformers including a. a driving shaft (12,18); b. a driven shaft (13); c. a gear (15) arranged in coaxial relation to and rotatable relative to said driven shaft (13) and driven by said driving shaft (12,18); d. a hub member (221) fixedly mounted on said driven shaft (13) for joint rotation with said driven shaft (13) and including a pair of abutment surfaces (220) projecting substantially radially outwardly from said driven shaft (13); e. a coupling member (26) having a surface in abutting relation with said hub member (221) and being loosely mounted on said driven shaft (13), said coupling member (26) having abutment means (30) cooperating with said abutment surfaces (220) of said hub member (221) to limit the freedom of relative rotary motion of said coupling member (26) on the one hand, and said hub member (26) and said driven shaft (13), on the other hand, f. normally ineffective latching means (31,29) for said coupling member (26) movable from an ineffective position to an effective position thereof and compelling in said effective position by positive mechanical action cessation of the rotary motion of said coupling member (26); and g. combined latching and torque-transmitting means (20,21,22,23) normally effective to transmit torques from said gear (15) to both said hub member (221) and said driven shaft (13), said combined latching and torque-transmitting means (20,21,22,23) including means (250) responsive to said cessation of said rotary motion of said coupling member (26) to render said combined latching and torque-transmitting means (20,21,22,23) ineffective to cause cessation of transmission of torques from said gear (15) to both said hub member (221) and said driven shaft (13) upon said cessation of said rotary motion of said coupling member (26).
 17. A gear drive for tap-changing regulating transformers as specified in claim 16 wherein said combined latching and torque-transmitting means include a. a substantially annular latching element (21) surrounding said driven shaft (13) and having an abutmeNt means (250) projecting axially outwardly from a plane defined by said latching element (21) and arranged to be engaged by said abutment means (30) of said coupling member (26), said latching element (21) being provided with means (21'',23,22) pivotally connecting said latching element (21) to said hub member (221), and said latching element (21) being further provided with a pair of latching surfaces (210) arranged to opposite sides of said means (21'',23,22) pivotally connecting said latching element (21) to said hub member (221), and wherein b. said gear (15) is provided with a torque-transmitting projection (20) on the end surface thereof adjacent said annular latching element (21) cooperating with said pair of latching surfaces (210) thereof.
 18. A gear drive as specified in claim 18 wherein said abutment means (250) is hollow and houses a brake mechanism including a spring (24) and brake block (25) biased by said spring (24) and frictionally engaging said end surface of said gear (15) adjacent said annular latching element (21).
 19. A gear drive as specified in claim 16 including a. a gear housing (10) and a cover (11) therefore having an aperture on one side thereof, said gear (15), said hub member (221) and said combined latching and torque-transmitting means (20,21,22,23) being arranged inside of the space bounded by said gear housing (10) and said cover (11), and said coupling member (26) being arranged in part inside of aid space and in part outside of said space and projecting through said aperture in said cover; and b. a mechanical power transmission (34,35,33) arranged outside of said space, said transmission being operated by one end of said driven shaft (13) projecting through said coupling member (26) to the outside of said space and said transmission (34,35, 33) controlling said normally ineffective latching means (31, 29) to render said normally ineffective latching means effective upon a predetermined number of revolutions of said driven shaft (13).
 20. A gear drive for tap-changing regulating transformers including a. a driving shaft (12,18) supporting a driving gear (16,17); b. a driven shaft (13); c. a gear (15) arranged in coaxial relation to said driven shaft (13), rotatable relative to said driven shaft (13) and driven by said driving gear (16,17); d. a hub member (221) fixedly mounted on said driven shaft (13) for joint rotation with said driven shaft (13); e. a coupling member (26) loosely mounted on said driven shaft (13) in torque-transmitting relation with said hub member (221); f. cooperating abutment means (220,30) on said hub member (221) and on said coupling member (26) for limiting the amount of relative rotary motion of said hub member (221) and of said coupling member (26); g. normally ineffective latching means (31,29) for said coupling member (26) movable from an ineffective position to an effective position thereof and compelling in said effective position by positive action cessation of rotary motions of said coupling member (26) about said driven shaft (13); h. means (34,35,33) responsive to the rotary motion of said driven shaft (13) for moving said normally ineffective latching means (31,29) from said ineffective position to said effective position; i. combined latching and torque-transmitting means (20,21,22,23) interposed between said gear (15) and said hub member (221) for torque transmission from said gear (15) to said hub member (221); and j. means under the control of said coupling member (26) engaging said combined latching and torque-transmitting means (20,21,22, 23) upon said cessation of rotary motion of said coupling member (26) about said driven shaft (13) and thereby unlatching said combined latching and torque-transmitting means (20,21,22, 23) to preclude further torque transmission from said gear (15) to said hub member (221).
 21. A gear drive as specified in claim 20 wherein said combined latching and torque-transmitting means include a. a substantially annular latching element (21) surrounding said driven shaft (13) and having a pair of latching surfaces (210) engageable by cooperating latching surfaces (20) on said gear (15); and b. a pin (23) pivotally connecting said annular latching element (21) and said hub member (221) and wherein c. said coupling member (26) is provided with an abutment (30) arranged to engage a cooperating abutment surface (250) on said annular latching element (21) to cause disengagement of one of said pair of latching surfaces (210) of said annular latching element (21) from said cooperating latching surfaces (20) on said gear (15).
 22. A gear drive as specified in claim 21 including means in the nature of a friction brake (24,25) supported by said annular latching element (21) establishing a frictional connection between said annular latching element (21) and said gear (15). 